(1) Field of the Invention
The present invention relates to a lining method using clad pieces and a clad piece adapted to be used for the method.
(2) Description of the Prior Art
Tanks for holding chemicals are often lined with highly corrosion-resistant metal. These liners are often a complicated process, for example the copper surface of a tantalum-copper clad is produced by an explosive adhesion process wherein the clad is adhered to the steel of a tank wall by the pressure of an explosion.
It is generally necessary in the explosive adhesion process that the metal sheet forming the surface layer of a clad has a thickness of at least 2 mm and the liner of the clad has a thickness of at least about 9-12 mm. However, when a surface layer of a clad is formed of an expensive and high-performance material, such as tantalum, about 0.1 mm thickness is used; and when a liner of a clad is formed of copper, about 1 mm thickness is used. Therefore, rolling and other steps requiring working of the metal are necessary in order to obtain the desired sheet thicknesses in the resulting clad. Moreover, in the welding of the clads produced by explosive adhesion, it is necessary that the tantalum surface layer located along the edge of the liner be scraped prior to the welding of the fellow clads. After welding the clads, the welded portion is covered with a thin tantalum strap and then is welded to the tantalum surface layer. However, tantalum has a melting point (2,996.degree. C.) remarkably higher than the melting point of copper (1,083.degree. C.), and therefore during the welding of the thin tantalum strap, the copper sheet is melted and alloyed with tantalum thereby deteriorating the performance of the tantalum surface layer. Therefore, welding of fellow conventional clads is very difficult and impractical.